In order to eliminate impurities from raw liquid while executing discoloration, deodorization, and purification processes, conventionally, adsorption and reaction processes with activated charcoal, oxidation process with catalyzer, and ion-exchange reaction with ion-exchange resin, are respectively executed. Typically, a contact filtration equipment is used to eliminate impurities from raw liquid by applying adsorbent, catalyzer, and ion-exchange resin. This conventional filtration equipment adsorbs impurities by initially mixing pulverized adsorbent component with raw liquid followed by a stirring process to generate suspension. When absorption reaches equilibrium, treated liquid is separated from adsorbent component via a filtration process. Whenever applying adsorbent comprising fine particles, a precoat filtration device is used to separate the treated liquid from adsorbent component. In this case, initially, auxiliary precoating agent such as diatomaceous earth is precoated on the filtration device to separate the treated liquid from adsorbent component.
When operating the above-cited conventional filtration device, the finer the particle size of the adsorbent, the faster the adsorption and greater the absorptive capacity. Nevertheless, because of difficulty to fully separate treated liquid from adsorbent component, there is a certain limit in regard to the minimizable range of particle size of usable adsorbent. Furthermore, while using the precoat filtration device to separate treated liquid from ultra-fine adsorbent, auxiliary precoating component adhered to adsorbent component inhibits the main adsorbent component from being regenerated, and therefore, once-used adsorbent is compulsorily discarded as useless waste blended with auxiliary precoating agent.